An antenna array usually comprises a plurality of individual antennas used to emit electromagnetic waves. The phases of the electromagnetic waves emitted by the individual antennas are adjusted for each antenna such that the whole antenna array is deemed to be one single antenna element emitting an electromagnetic signal having certain characteristics.
The antenna array may be used as a part of a test system in order to test a device under test such as a communication device under far field conditions inside a small test chamber of the test system. If a large distance is provided between the transmitter and the receiver, the emitted electromagnetic wave corresponds to a plane wave. Thus, far field conditions of an antenna element relate to plane waves at the location of the receiver. However, the usage of an antenna array provides the opportunity to simulate far field conditions even though the distance is small since the electromagnetic signal transmitted by the antenna array corresponds to a plane wave at a certain distance. Accordingly, an antenna array is used wherein the antennas of the antenna array are controlled such that they generate electromagnetic waves which together form a plane wave at the location of the device under test, for instance. Thus, it is possible to measure and analyze the receiving and transmission properties of the device under test under far field conditions even though a small distance is provided between the antenna array and the device under test.
Usually, the arrangement of the plurality of antennas within the antenna array is provided such that optimal performances are obtained. Accordingly, the antenna array is suitable for a specific application, in particular a certain distance between the antenna array and the device under test which in turn corresponds to a certain frequency of the plane wave and/or a specific size of the device under test.
However, the user of such a test system, in particular such an antenna array, also wants to test devices which may have different sizes and/or test the same device with different frequencies. Thus, another antenna array has to be installed and calibrated in order to perform these further tests being of interest. This results in a lot of additional effort which in turn increase the costs of the measurements.